The 43-year-old actress might be a Hollywood superstar, but she insists her three children - 18-year-old Mia, whose father is her first husband Jim Threapleton, 15-year-old Joe, whom she has with ex-husband Sam Mendes, and five-year-old Bear, with current spouse Ned Rocknroll - aren't ''over-privileged'', because she makes sure they understand how ''impoverished'' their ancestors were.

She said: ''I come from a long line of impoverished people on both sides of my family, which perhaps explains why I've tried to instil my parents' values into my kids. People never believe me, but my children aren't over-privileged. We just don't live like that. They are very balanced. Humble.''

The 'Titanic' star is the latest celebrity to take part in the BBC programme 'Who Do You Think You Are?', in which stars uncover the secrets of their ancestry, and discovered her family tree connected her to Sweden, where her ancestors lived in poverty.

Speaking about the discovery, Kate said she was proud to have come from an impoverished family, because her ''socialist'' parents ''frowned upon the wealthy''.

She added: ''I would have been upset and disgusted if I had come from wealth or royalty. There was never any money in our family, but I always felt very fortunate because I came from a lovely, wonderful, loving family.''

And Kate also insisted that realising her family had emmigrated from Sweden to the UK made her ''think about this world we live in''.

The 'Eternal Sunshine of the Spotless Mind' star told the Radio Times magazine: ''[It] basically means I'm an immigrant. It really made me think about this world we live in. Refugees, immigrants - we're going to have to stop using these words, as if those people are subhuman.''